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Neoproterozoic crustal geodynamics of the Northwest Indian block as revealed in magmatic episodes
26 septembre 2017 @ 10h30 – 12h30 CET
The NW Indian block exposes Grenvillian age to late Neoproterozoic, predominantly granitic, rocks along the western margin of NE-trending Proterozoic Aravalli – Delhi Fold Belt that encompass a critical time interval from Rodinia assembly and breakup. The region hold a position in paleogeographic reconstructions of supercontinent Rodinia and located along its western margin in most paleogeographic reconstructions. The NW Indian block comprises the Archean – Proterozoic Banded Gneiss – Bundelkhan Craton in the east and Neoproterozoic – Pahnerozoic Marwar block in the west, both separated by the NE-trending Proterozoic Aravalli – Delhi Mobile Belt (ADMB). The Marwar Block amalgamated with the ADMB at ~1 Ga and this crustal convergence also initiated ophiolite obduction (Phulad Ophiolite Suite). The ocen floor closure and continent – continent collision event is also manifested in the emplacement of 967 Ma calc-alkaline Sendra Granites. Subsequent tectonomagmatic event, the Erinpura Granite intrusions, spans between 870 – 800 Ma and marks end of the Delhi Orogeny. The most extensive event is the 770 – 750 Ma predominantly felsic magmatism called the Malani Igneous Suite (MIS). The MIS comprise predominantly felsic volcano-plutonic rocks (rhyolite – ignimbrite, peraluminous – perlakaline granites, felsic and mafic dykes).
The MIS has been traditionally described either as Anorogenic, rift-related or plume related and more recently as an Andean type event. Recent paleomagnetic data suggest a much northerly paleoposition for the NW Indian block than proposed earlier. End Proterozoic event in this region is the deposition of sand – shale – carbonate sediments of Marwar Supergroup where uppermost unit has been assigned an Early Cambrian age.